1. Field of the Invention
The invention relates to an apparatus for continuous corrugation of a metallic tube, which apparatus has a tool holder, which can rotate about the initially smooth tube and has a tool which is mounted eccentrically with respect to the tube and forces a corrugation into the tube during operation of the apparatus, which corrugation runs transversely with respect to the longitudinal direction of the tube, and which tool has a withdrawal device for movement of the tube in its longitudinal direction, in which a first hollow shaft is attached to the tool holder, projects in the pulling-off direction from it, surrounds the tube after the corrugation process and can be rotated about its axis with the tool holder by an electric motor, and in which the unit comprising the tool holder and the first hollow shaft is mounted such that it can move in the axial direction (EP 1 084 774 B1).
2. Description of Related Art
Because of the corrugation, tubes such as these can on the one hand be bent well and on the other hand are robust in respect of forces acting on them in the radial direction. They can be used to transport fluid media, or else as casings or conductors for electrical and/or optical cables. A corresponding tube may be composed of steel as a casing which is used to protect a cable core. It is advantageously used as a conductor in radio-frequency cables. It is then advantageously composed of copper.
In the apparatus according to EP 1 084 774 B1, which was cited initially, the first hollow shaft, which is attached to the tool holder, at the same time forms the rotor of the driving electric motor, whose stator is fitted to fittings of the apparatus. During operation of the apparatus, the first hollow shaft is therefore rotated about its axis as part of the electric motor. In the process, it drives the tool holder, which is firmly connected to it and whose tool forces the corrugation into the tube, which is moved continuously through the tool holder, in its axial direction. The tool holder with the connected hollow shaft as well as the stator of the electric motor are combined in this known apparatus to form one unit, which is mounted such that it can move in the axial direction. This makes it possible to compensate for discrepancies in the corrugated means from a predetermined central position, which discrepancies can occur during continuous manufacture. The weight of the described unit is relatively high, as a result of which a relatively large amount of complexity is required for the capability to move it easily.